1. Field of the Invention
This invention relates to novel crystalline borosilicates, catalysts containing such borosilicates, and a method for preparing such catalysts. More particularly, this invention relates to hydrocarbon-conversion catalysts that contain the crystalline borosilicates, a method for preparing such catalysts, and various hydrocarbon conversion processes using such crystalline borosilicates. Patent art that is relevant to such borosilicates can be found in U.S. Patent Classes 423-326, 252-458, and 260-668.
2. Description of the Prior Art
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic capabilities for many hydrocarbon processes. Zeolitic materials, often referred to as molecular sieves, are ordered porous crystalline aluminosilicates having a definite structure with large and small cavities interconnected by channels. The cavities and channels throughout the crystalline material are generally uniform in size allowing selective separation of hydrocarbons. Consequently, these materials in many instances have come to be classified in the art as molecular sieves and are utilized, in addition to the selective adsorptive processes, for certain catalytic properties. The catalytic properties of these materials are also affected, to some extent, by the size of the molecules which are allowed selectively to penetrate the crystal structure, presumably to be contacted with active catalytic sites within the ordered structure of these materials.
Generally, the term "molecular sieve" includes a wide variety of positive-ion-containing crystalline materials of both natural and synthetic varieties. They are generally characterized as crystalline aluminosilicates, although other crystalline materials are included in the broad definition. The crystalline aluminosilicates are made up of networks of tetrahedra of SiO.sub.4 and AlO.sub.4 moieties in which the silicon and aluminum atoms are cross-linked by the sharing of oxygen atoms. The electrovalence of the aluminum atom is balanced by the use of positive ions, for example, alkali-metal or alkaline-earth-metal cations.
Prior art developments have resulted in the formation of many synthetic crystalline materials. Crystalline aluminosilicates are the most prevalent and, as described in the patent literature and in the published journals, are designated by letters or other convenient symbols. Exemplary of these materials are Zeolite A (Milton, in U.S. Pat. No. 2,882,243), Zeolite X (Milton, in U.S. Pat. No. 2,882,244), Zeolite Y (Breck, in U.S. Pat. No. 3,130,007), Zeolite ZSM-5 (Argauer, et al., in U.S. Pat. No. 3,702,886), Zeolite ZSM-11 (Chu, in U.S. Pat. No. 3,709,979), Zeolite ZSM-12 (Rosinski, et al., in U.S. Pat. No. 3,832,449), and others.
Relevant art is the above U.S. Pat. No. 3,702,886, in which Argauer, et al., disclose the crystalline aluminosilicate Zeolite ZSM-5 and the method for making the same. This patent teaches the production of a zeolite wherein aluminum or gallium oxides are present in the crystalline structure, along with silicon or germanium oxides. A specific ratio of the latter to the former is reacted to produce a class of zeolites designated ZSM-5, which is limited to crystalline alumino- or gallo-silicates or germanates and which has a specified X-ray diffraction pattern. The above ZSM-11 and ZSM-12 patents are similarly limited to crystalline alumino- or gallo-silicates or germanates, also having specified X-ray diffraction patterns.
As shown by Haag, et al., in U.S. Pat. No. 3,856,871, by Morrison, in U.S. Pat. No. 3,856,872, by Burress, in U.S. Pat. No. 3,856,873, and by Hayward, in U.S. Pat. No. 3,856,874, such ZSM-type aluminosilicates are used suitably for the isomerization of xylenes.
Manufacture of the ZSM-type materials utilizes a mixed base system in which sodium aluminate and a silicon-containing material are mixed together with sodium hydroxide and an organic base, such as tetrapropylammonium hydroxide or tetrapropylammonium bromide, under specified reaction conditions, to form the desired crystalline aluminosilicate.
Dwyer, et al., in U.S. Pat. No. 3,941,871, claim and teach an organosilicate having very little aluminum in its crystalline structure and possessing an X-ray diffraction pattern similar to the ZSM-5 composition. This patent is considered relevant art.
Another relevant patent is U.S. Pat. No. 3,328,119, wherein Robson considers a synthetic crystalline aluminosilicate containing a minor amount of boria as an integral part of its crystal framework. This reference has been cited by the Examiner during the prosecution of the above-mentioned applications U.S. Ser. No. 819,974, now abandoned, and U.S. Ser. No. 836,403 now abandoned.
Additional relevant art comprises U.S. Pat. Nos. 3,329,480; 3,329,481; 4,029,716; and 4,078,009. Young, in U.S. Pat. Nos. 3,329,480 and 3,329,481, discloses "zircono-silicates" and "titano-silicates", respectively. Kaeding, in U.S. Pat. Nos. 4,029,716 and 4,078,009, discloses a crystalline aluminosilicate zeolite having a silica-to-alumina ratio of at least about 12 and a constraint index within the approximate range of 1 to 12, and having combined therewith boron in an amount of at least about 0.2 weight percent as a result of reaction of the zeolite with a boron-containing compound.
Unland, et al., in U.S. Pat. Nos. 4,115,424 and 4,140,726 disclose an improved alkylation catalyst that comprises a crystalline aluminosilicate exemplified by a type X- or Y-zeolite, which catalyst includes potassium, rubidium, and/or cesium cations and contains boron and/or phosphorus. The aluminosilicates are modified to have the potassium, rubidium, and/or cesium cations and the boron and/or phosphorus present. The boron or phosphorus components can be incorporated by inclusion in an ion exchange solution, or by subsequently utilizing a solution of such component as a slurrying medium for catalyst particles or as an impregnating medium to be absorbed in the catalyst.
Plank, et al., in U.S. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253, disclose the suspension of a molecular sieve material in a matrix of a refractory inorganic oxide and its distribution throughout said matrix. The preparation and use of cation-exchanged molecular sieves are considered.
The present invention is directed to catalysts that comprise crystalline borosilicates and that can be used for the conversion of hydrocarbon streams, e.g., the isomerization of xylene feedstocks, and to the preparation of such catalysts.